1. Field of the Invention
This invention relates to adhesives prepared from metabolically-acceptable polyisocyanate or polyisothiocyanate monomers. More particularly, the present invention is concerned with surgical adhesive polymers derived from these polyisocyanate monomers which do not metabolize to toxic products.
2. Brief Description of the Prior Art
In recent years there has developed increased interest in replacing or augmenting sutures with adhesive bonds. The reasons for this increased interest are many but those most evident are:
(1) the potential speed with which repair might be accomplished;
(2) the ability of a bonding substance to effect complete closure, thus preventing seepage of fluids;
(3) the possibility of forming a bond without excessive deformation of tissue, and
(4) possible improvement in repair of tissue too weakened by disease or age to permit effective suturing.
Studies in this area, however, have revealed that, in order for surgical adhesives to be accepted by surgeons, they must possess a number of properties. First, they must exhibit high initial tack and an ability to bond rapidly to living tissue. Secondly, the strength of the bond should be sufficiently high to cause tissue failure before bond failure. Thirdly, the adhesive should form a bridge, preferably a permeable flexible bridge. Fourthly, the adhesive bridge and/or its metabolic products should not cause local histotoxic or carcinogenic effects.
A number of adhesive systems such as alkyl cyanoacrylates, polyacrylates, maleic anhydride/methyl vinyl ethers, epoxy systems, polvinyl alcohols, formaldehyde resins and isocyanates have been investigated as possible surgical adhesives. None has gained acceptance because each fails to meet one or more of the criteria noted above. The principal criticism of these systems has been the potential toxicity problems they pose. In the case of adhesives based on conventional isocyanates, for example, the production of aromatic and aliphatic diamines by metabolism could lead to local histological reactions at minimum, and possibly to even more serious systemic toxicity.
It is an object of the invention to provide novel metabolically-acceptable polyisocyanate adhesives, including polyisothiocyanate-based adhesives and in particular metabolically-acceptable surgical adhesives.
Yet another object of the invention is to provide metabolically-acceptable surgical adhesives which are biodegradable.
A further object of the invention is to provide a method for closing wounds in living tissue by use of novel, metabolically-acceptable surgical adhesives.
An additional object of the invention is to provide metabolically-acceptable adhesives low in toxicity as a consequence of their physical properties.